Oral malignant melanomas (OMM) in dogs have a high potential to metastasize or spread. While OMM is responsive to immunotherapy, responses are varied and difficult to predict, and only a subset of patients respond to immunotherapy. Therefore, it is vital to identify dogs with the best chance of responding to immunotherapy, understand which dogs may not respond and why, and to discover new therapeutic targets to increase response rates. Current high throughput methods for profiling the immunology of the tumor microenvironment cannot define cells nor can they investigate cell functions that are critical for determining immunologic profiles. This study’s objective is to identify T regulatory cells, a type of lymphocyte, that suppress the immune response, within the tumor microenvironment of OMM. The investigators will concurrently determine cellular function by investigating intracellular cytokine production utilizing a highly sensitive and specific in situ hybridization technology known as RNAscope. Unlike current methods of detection, this technology can detect multiple cell markers simultaneously, identifying the cells of interest. This technology has the potential to define prognostic and predictive factors for immunotherapy response to assist veterinarians and clients in determining the best treatment option for their dog.